Once-through vapor generator



United' StS Patent 2,977,937 ONCE-THROUGH VAPOR GENERATOR KarlDeitlhaser, Munich, Germany, assigner to Durrwerke Aktiengesellschaft,Ratingen, Germany, a corpuration of Germany Filed am. s, 195s, ser. No.707,697 Y [s claims. (Cl. 1225-240) This invention relates in general toimprovements in forcedflow, once-through vapor generators and moreparticularly to the .construction and operation of a plural Vchambered,cyclone furnace tired, forced flow, oncethrough vapor generator designedfor wide load range furnace operation.

`"icc invention are pointed out with particularity in the lclaimsannexed to and forming a part of this specification. For

nace above the ash fusion temperature and thereby keep VVthe slagliquid. If the slag freezes it will prevent proper Because of thisinherent limiting characteristic cyclone furnaces have a load rangeVy onthe Y order of 3 to l. y

Additionally,lin forced flow once-through yvapor generators there arecertain vaporizable fluid velocity limitations Which affect the width ofits control range. The amount of heat input to the tube system demandsthat certain minimum tube flow velocities be maintained regardless ofvapor generatorload to prevent tube .burnnut. In turn, the `maXimumloadto which any given flow trolled velocity range lof approximately 3 or 4to l which is similar in scope to\ the load range required forcyclonefurnace tiring.

In order Vtc use a cyclone furnace tired, forced flow,

a better understanding of the invention, its operating advantages andspecific objects attained by its use, reference Y should be had to theaccompanying drawing and descriptive matter in which a certain specificembodiment of the invention is illustrated and described. l

Referring to the drawing, which shows a schematic diagram lof anembodiment of the invention, a setting 10 for a forced flow,once-through vapor generator is separated by division walls 18A, 18Binto individual heating gas chambers 12A, 12B, 12C. Each of theindividualv chambers 12A, 12B, 12C has a once-through vapor generatingtube system 14A, 14B, 14C and a separately red cyclone furnace l6A, 16B,16C. The arrangement of the cyclone furnace as embodied in the inventionis disclosed in Patent No. 2,594,312. A Vaporizable liquid is suppliedto each of the vapor generating tube systems 14A, 14B, 14C at asubstantial positive pressure by a single feed pump 24. The pump 24receives its supply of Vaporizable liquid from a feed liquid storagetank 22.

The liquid to be vapjorized is delivered by the pump 24 to a conduit 26which is trifurcated and forms the 'ow passageways 2SA, 28B, 28C. Valves30A, 30B, 30C are located in the ow passageways 28A, 28B, 28C andcontrol the flow of Vaporizable liquid to the separate once-throughvapor generating tube systems 14A, 14B, 14C. lf the valves 30A, 30B, 30Care open the vaporizable .liquid enters the once-through tube systemsand Vpasses first through the economizer sections 32A, 32B,

' steam temperature. The vaporizable liquid upon leaving .the economizersections then flows serially through tubes vwhich form the walls `of theseparately fired cyclone furnaces MA, 16B, MC and through final -vapcrgenerating tube sections 34A, 34B, 34C. n Y

In flowing throughythe wall tubes of the cyclone fur- -naces and thefinal Vapor generating tube sections the once-through vapor generatorforwide load range opera- A, f tion the limitations `on load-,rangecaused by. the use of ,i

' a cyclone furnace and Vby Vthe need to preventtubeburnout must beOvercome. ltfhas'been known teV Vuse a 'forced newprice-through vaporgenerator tired by a plurality'jof cyclone furnaces. While this,"yarrangement perstruction it, nevertheless, resultsin overheatingandfailure` mits anincreasedload rangeforthe combustion systemlidonee-through vapor generators of conventional coni.v

v ...Of the tube system because the ilc'wr'velocities fall belowl-th=epermissible limits tolproperly cool the tubes;

Therefore, it is therpurpose` of the 'presentinyention Y to'gprovidea"once:throughv Vapc'nr` generator tired a I plurality of cyclonefurnaces whichcperates overfajwide 'f load rangei lThe setting'Of-the'unit ini tbefpresentginvensuperheated vaporgjgenerated withintneindividual `vapor l' ,'generatiiig and` superheating systeinsdsdeliveredjtoa haracterrze the Avaporizable liquid receives the finalheat required'fcr vaporization. `The vaporized uid next passes insuccession throughV primary superheaters 38A, 38B,` 38C and secondarysuperheaters A, @13,40 whereinitf receives the nal degree of superheat vThe superheated vapor tlien passes frcmthe once` through vaporgenerating tube'systeins 14A,14B,1l4IC within the individual chambers12A, 12B, :l2C'and flows through the parallelconduits 42A, 42B, 42C.external 'of the setting 1t), to 'a common high pressure vapor outlet,line Sil.. -Valves 44A, 44B, 44C are located in the ccn- "duitsllZA,242B, 4420m control the flow of vapor therethrough. A main. cut-oitvalve 52'is provided in they common vaporoutlet line 50. The superheatedAvapcr flows through the common discharge line tc* a liigh presi ,fsureturbinefi whereinit expandsto dofwcrlcand leaves fat a reduced pressureand temperature.- The reduced pressure vapor passes fromA the highpressure turbine Vrgtbr'ougl'r a ow passageway 56. The ow passagewayASeis ,trifurcated te form parallel ow passageways 58A,

58B, SSC which reenter theindividual chambers 112A, aan, 12e; valvesssn, ses, @C are'lceated inv nie Y 'passageways' 58A, SSWBSSC to`control the flow of vaporv .v f3 therethroiigh.` The reducedpressureyapcr passes through 65; the flow passageways `S8A', 58h53@tofreheaters 62A,

v1 62B, 62C located Withinl the individual heating gas chami "ber's'l'Z,312B, l12C where-the vapor is` again heated.' f The `retreated,vap'orleavesthe reheaters 562A,f62l3,f62C

'throughdlav common low VpressureV outlet line" 65 andzlis yAdelivered'toja low pressure'turbine156.V Thereheated v vapor deesVfurther wcrkfwithin the low pressure. turbine` nd theufiows to lacondeuser70 through accnduit 67.1' v

After the vaporized uid is condensed it is returned to the feed liquidstorage tank 22 by way of a conduit 72.

The embodiment of the invention as illustrated in the drawing showsthree individual heating gas chambers 12A, 12B, 12C within a singlesetting 10 each having its own separately red cyclone furnace 16A, 16B,16C and forced flow, once-through vapor generating tube system 14A, 14B,14C. As has already been stated a single cyclone furnace fired vaporgenerator operates on a load range of 3 to l, however, the embodimentillustrated widens the load range of a cyclone furnace tired vaporgenerator to 9 to 1 without the previously encountered limitations.

At full load the three separately fired cyclone furnaces and theircompanion once-through vapor generating tube systems operate at maximumoutput. As the demand on the vapor generating unit decreases the firingrate of the individual cyclone furnaces must be either reduced or one ormore of the cyclone furnaces taken out of operation. Since a single feedpump 24 supplies the vaporizable fluid to all of the once-through vaporgenerating tube systems 14A, 14B, 14C the velocity of the vaporizableuid in each of the operating tube systems is uniform. Therev fore, sincethe iiow velocities are uniform the tiring rate of the cyclone furnaces16A, MB, 16C must be kept uniform, Where more than one cyclone furnaceis being operated, so that vapor is generated at a uniform temperatureand pressure. For example, if the vapor generating unit is operating at75% of its maximum output the three cyclone furnaces each deliverheating gases to the system at 75 of their maximum load and in turn thefeed pump is adjusted to deliver vaporizable liquid to the tube systenisat a velocity suiiicient to generate vapor at the temperature andpressure required. As the demand decreases below two-thirds of themaximum output of the vapor generating unit, it becomes possible to cutout one of the once-through vapor generating tube systems, and so toowhen the demand further decreases to below onethird, it is possible tocut-out a second vapor generating tube system.

To illustrate reduced operation of the vapor generating unit if it isoperating at say 60% of its maximum output two cyclone furnaces IGA, 16Bcan be kept in operation Whilethe third cyclone furnace 16C is shutdown. To achieve an overall vapor generatingoutput of 60% of maximum thetwo cyclone furnaces must deliver heating gas to the individual chambersZA, 12B at 90% of their maximum load. The feed pump is adjusted tosupply the vaporizable liquid to the tube system 14A, 14B at 60% of itsfull load capacity and at a velocity required by the vapor generatingtube systems 14A, 14B to operate at 90% of their full load. The valves30C and 44C are closed to shut off the vapor generating tube system 14Cand the valve 60C is closed to cut out the re- 'heater 62C. Accordingly,the vapor generator described ,herein will satisfy any load requirementwithin a range of 9 to l by controlling the operation of the feed pumpand the firing of the separate cyclone furnaces. In addition, though theload range .is widened therange of flow -velocities in the tube systemswill remain unchanged due to the novel vapor generating tube systemarrangement.

provides a means for using a cyclone furnace fired, forcedy cyclonefurnace firing means and vapor generating systo the number of individualheating gas chambers which make up the vapor generating unit. Though,the construction of the present invention permits the load range to beincreased the velocity range is not affected and remains the same foreach individual vapor generating tube system thereby avoiding theproblem of tube failure due to overheating.

Therefore, the present invention permits a much wider load range in theuse of a cyclone furnace fired, forced flow, once-through vaporgenerating system without the usually accompanying problem of tubefailure at lower loads which result from reduced flow velocities.

While in accordance with the provisions of the statutes I haveillustrated and described herein the best form of the invention nowknown to me, those skilled in the art 'will understand that changes maybe made in the form of the apparatus disclosed without departing fromthe spirit of the invention covered by my claims, and that certainfeatures of my invention may sometimes be used to advantage without acorresponding use of other features.

What is claimed is:

l. In a forced flow once-through vapor generating and superheating unitadapted for wide load range operation, walls defining a setting,division walls arranged to divide said setting into separate individualadjoining heating gas chambers, a separately red cyclone furnace foreach of said chambers arranged to supply heating gases only to itscorresponding chamber, tube means forming separate parallel forced owonce-through vapor generating and superheating flow paths in each ofsaid chambers for effecting a continuous parallel llow of liquid throughsaid flow paths as the liquid is vaporized and superheated, means forsupplying a vaporizable liquid to all of said parallel flow paths from acommon supply, individual valve means to control the flow of vaporizableliquid through each of said flow paths, said valve means locatedexteriorly of said setting, and means for delivering the vaporsuperheated in said parallel flow paths to a common discharge point.

2. In a forced ow once-through vapor generating and superheating unitadapted for wide load range operation, walls defining `a setting,division walls arranged to divide said setting into separate individualadjoining heating gas chambers, a separately red cyclone furnace foreach of said chambers arranged to supply heating gases Ionly to itscorresponding chamber, tube means forming separate parallel forced owonce-through vapor generating and superheating flow paths in each ofsaid chambers for effecting a continuous parallel flow of liquid throughsaid flow paths as the liquid is vaporized and superheated, said tubemeans for each of said flow paths comprising an Y l economizer section,a fluid heating section a portion of which formsthe walls of saidcyclone furnace, a primary superheater and a secondary superheater,means for supplying a vaporizable liquid to all of said parallel flowpaths from a commonl supply, individual valve means to control the flowof vaporizable liquid through each of said ow paths, said valve meanslocated exteriorly of said setting, and means for delivering the vaporsuper- Y heated in said parallel flow paths to a common dischargeTherefore the construction of the present invention l point.l A

` 3Q In a forced flow once-through vapor generating, superheating andreheating V'unit adapted for wide load range operation, walls dening asetting, division walls arranged to divide said setting into separateindividual adjoining heatinggas chambers, a separately fired cyclonefurnace arranged for eachrof said chambers to supply 'heating gases onlyto its corresponding chamber, tube Atem though theyall have acommonsource of vaporizable liquid and a common 'point of discharge.Therefore,l the l through vapor generator to be increased in directrelation means forming separate parallel forced flow once-through vaporgenerating, superheating and reheating iiow paths ineach of saidchambers for `effecting a continuous parallel How-of liquid through saidflow vpaths as the liquid is vaporized superheated and reheated, meansforV supplying 7,7 a vaporizable liquidvto allv of said parallel flowpaths from 6 `a common supply, individual valve means to control the2,557,569 Schutt June 19, 1951 ow of vaporizable liquid through each ofsaid ow paths, 2,709,424 Sifrin May 31, 1955 said valve means locatedexteriorly of said setting, a first 2,781,746 Armacost et al. Feb. 19,1957 common outlet line arranged to receive and to deliver the vaporsuperheated in said parallel ow paths to a irst 5 FOREIGN PATENTS commondischarge point, and a second common outlet 1,112,486 France Nov. 15,1955 line arranged lto receive and -to deliver the vapor reheated750,484 Great Britain June 13, 1955 in said parallel ow` paths to asecond common discharge point. OTHER REFERENCES References Citedin the1e 0f this Patent lo Gastpar: European Practice with Sulzer, OctoberUNITED STATES PATENTS 1953. pp 1345-1361 1,930,455 Hannum Oct. 10,1933

